Embodiments of the present invention relate to a fuse of a semiconductor device and a method for forming the same, and more particularly to a fuse of a semiconductor device using a metal contact, and a method for forming the same.
Numerous memory cells capable of storing data are contained in a semiconductor device, such as a memory device or a memory merged logic (MML). However, if any one of the memory cells contained in a semiconductor device is determined to be a defective or a failed memory cell, the whole memory device becomes a defective product, resulting in reduction in production yield. That is, although the failure occurs only in some cells of the semiconductor device, the entire semiconductor memory device is discarded as a defective product, resulting in far less efficiency in terms of production yield. In order to guarantee the high production yield of a memory device or a semiconductor device including memory cells, a repair function is needed. In accordance with a repair process for a semiconductor device, a defective memory cell is replaced with a redundancy memory cell. In order to replace a defective memory cell with a redundancy memory cell, a fuse is used. Therefore, a plurality of fuses is contained in the semiconductor device, and the fuses can be blown (or severed) by a laser spot. In addition, fuses can be selectively removed according to a test result of the semiconductor device.
In a repair method using a redundancy cell, a redundancy word line, which substitutes for a normal word line, and a redundancy bit line, which substitutes for a normal bit line, are pre-installed per cell array. That is, if a defective or a failed part is found in a specific cell, a normal word line including the failed part or a normal bit line including the failed part can be replaced with a redundancy word line or a redundancy bit line. For this purpose, the memory device includes a specific circuit configured to replace an address assigned to the defective cell with an address assigned to the redundancy cell. Therefore, by using the above-mentioned repair method based on a redundancy cell, if an address signal corresponding to the defective cell is input, the redundancy cell is activated instead of the defective cell.
A popular repair method replaces an original address path with a substitute path by burning off the fuse coupled to the original address path with laser spots. Therefore, a typical memory device includes a fuse unit that is designed to be cut by a laser spot. In the fuse unit, a portion to be blown by a laser spot is referred to as a fuse, and a portion surrounding the fuse is referred to as a fuse box.
A typical fuse is generally formed as a line-type metal line. A fuse formed of aluminum is vulnerable to oxidation and shows a poor contact characteristic. A Cu fuse is generally formed by a damascene process. However, when Cu is subjected to a damascene process, it tends to migrate into another device element, causing an electrical short.
The area occupied by a fuse in a semiconductor device is relatively large in size when the fuse is formed in a line type. In order to reduce the area occupied by the fuse, fuse length may be shortened. In that case, however, when the target fuse is cut, a neighboring fuse is likely to be damaged as well, resulting in a failed or defective semiconductor memory product. Thus, it is difficult to reduce the size of a fuse in a line type to successfully perform the conventional repair method.